The prevalence of factor VII (FVII) deficiency in 267 Brazilian patients was estimated to be 4.1%, including one patient with significant bleeding, five with minor bleeding and five patients asymptomatic. Only one novel mutation 8926G <-- T (I140S) was seen in one patient. The other mutations were 10828G <-- A (R304Q) in three patients, 10846G <-- T (C310F) in one patient, and 10909G <-- A (G331D) in one patient. Except for one homozygous patient (C310F) with a severe deficiency, only one allele was affected in all other instances. An inverse association between F7 polymorphisms and FVII activity were found in these patients, as those with higher levels of FVII activity presented the genotype described in the literature as related to reduced FVII activity. As the R304Q mutation was the most frequent in these patients, and may be associated with an asymptomatic form of the disease, particularly in Blacks, we examined this mutation and FVII activity in 49 Blacks and 49 Caucasian blood donors with no clinical bleeding. None of the individuals showed the R304Q mutation, and FVII activity was normal in all of them, thus indicating that FVII deficiency is not common in normal individuals of these two ethnic groups in Brazil. This is the first study in South America to examine the prevalence and molecular basis of FVII deficiency, including the description of a novel mutation.